With the increasing use of carbon fiber reinforced polymer (CFRP) composite structures in the aerospace and commercial aircraft industry, there is an increasing need for the advancement of efficient non-destructive evaluation (NDE) methods for the detection of composite damage. An especially dangerous form of damage results from lightning strike, which can induce thermal damage that is difficult to detect.
Typical inspection methods for thermal damage due to lightning strikes may include using ultrasonic instrumentation to determine whether damage, such as delamination, separation, and/or cracking, has occurred. Another method of inspection includes performing a Fourier transform infrared (FTIR) analysis of a spectral signal taken from the aircraft to correlate a visual inspection to heat damage for specific resin coatings. However, these methods are time consuming and may be inaccurate.
Other methods for detecting damage due to lightning strikes may involve determining a position of an initial strike point based on marks, discoloration, or damage caused by the initial lightning strike, and inspecting each component of the aircraft in proximity to the initial strike point. However, many of the components inspected may fall outside of a particular pathway followed by the electrical current from the lightning strike and are therefore unlikely to have been damaged. Because it is unknown which pathway the current may have taken, these components may be needlessly inspected. The inspections may also include time-consuming, expensive, and/or invasive dismantling processes. What is needed is a quick, reliable, and non-invasive method for determining a pathway taken by current from a lightning strike through a structure, and for determining the extent to which components along the pathway may have been damaged.